Power supply systems, in particular systems that generate power at frequencies of ≥1 MHz, are used for example for laser excitation, in plasma coating installations, or for induction applications. Power supply systems of this kind include amplifiers that generate the power that is supplied to the plasma coating installations, in induction applications or in laser excitation. There are, in principle, two concepts for controlling the power of an amplifier. In amplitude control, the output power of the amplifier is controlled by the amplitude of the input signal. Alternatively, the output power of the amplifier can be controlled by controlling the supply voltage of the amplifier. In this type of control, efficiency is kept relatively constant over a wide dynamic range. The amplifiers generally include at least one transistor which is connected to the supply voltage. Since the supply voltage is controlled, combinations of the driving voltage of the transistors and the supply voltage may arise, which subject the transistor to thermal stresses. In particular, the transistor is at risk of getting damaged in the process or having its service life significantly reduced.